I have a Chevy 2500 4x4 with push button 4x4 and Auto 4x4. The Truck shifts into 4x4 HI, Lo and Auto 4x4 fine. However 5-10 seconds later the 4x4 service light comes on. Also I cannot shift it out of 4x4 mode - pressing the 2w button has no effect regardless of if I am in Drive, Park or Neutral. However, If I turn off the truck and then turn it back on I can press the 2w button and it will go back into 2w mode just fine. This problem happens every time I try to go into any of the three 4w modes. The repeatability of it sounds like I'm doing something wrong. I should add that the truck has a 6" lift kit and 365/65R16 tires. It also has 74K miles.

I also have another problem with hard "clunk" shifting when the transmission is upshifting. It downshifts smooth. This only happens after the truck has run for 15 - 20 minutes. After turning off the truck for 10 minutes or so, like when getting gas, it will shift smooth as silk. Any ideas. Thanks for any help.

My guess the Transfer Case Encoder Motor is failing, sounds simular to the steps I recall to the failure of my 4wd.

The reason for the failure of the encoder motor on my 4wd was due to a bearing freezing on the sector shaft, this shaft connects to the encoder motor. The transfer case was cracked allowing water/salt to corrode the sector shaft bearing resulting in the encoder motor failure.

The transfer case crack... I don't think it was a crack from impact. I think it was a bad casting from the factory because of the location of the crack. JB weld in the crack fixed the problem along with a new sector shaft bearing and encoder motor.

i have a 2003 sierra my prob is my 4hi and 4lo dont engage but my auto 4 does work. when puttin into 4 lo it does gear down but front wheels do not engage could this be the encoder motor on the transfer case. any suggestions would be greatly apreciated. I can hear it is tryin to engage when i push either the 4 hi or 4lo buttons but like i said the front wheels dont engage

My 4 wheel drive went out this past week without any warning.I backed up to turn around and when I put it back into drive it made a grinding noise and the front wheels quit pulling. I tried several times and it would never engage again just the grinding, like gears not fully meshed. When I push the button it feels and acts like it engages 4hi and/or 4lo. I've read most of the posts on here and most just say theirs just quit working and it's the actuator motor. Is it possible that it is only partially engaging? Could it be the autolocking hubs? I haven't had time to check if the axles or drive line are turning, dark to work dark when I get home. I just need some advice for when I start on it this weekend. My truck has 172,000 on it and I've never had any other problems except fuel pump (twice). Any help in the right direction would be a greatly appreciated.

hey guys i got a 1999 1500,i started to drive the truck in 4x4 and the first 15 minutes i drove the car in 4x4 it was fine then there was clunk started in the front,i slowed down to about 5 mph and the clunk stoped.when driving in 2wd its fine but now im worried cause its snow season and i need 4wd.also it started when i made a turn if it makes a difference.

I found out what the grinding noise is. The splines in the front (4wd) diveshaft, where the 2 halves join, are slipping. I went to a couple of parts stores and they had never heard of that happening before. The shaft is $204 dollar with exchange, not that bad but, before I change it has anyone else heard of this happening? I would hate to change it if something else was the original problem and would just ruin another drivehaft. Any advise would be a big help.

Greetings Everyone! I am new to the group and looking for a little info regarding a recent problem with my truck. I have a 99 GMC Sierra 1500 Z71 with 195K. Recently while troubleshooting a drivetrain vibration I have found that the front driveshaft is not disengaging. The electronic 4WD works correctly and the front wheels disengage when switching to 2WD but the front driveshaft stays engaged and turning. Any suggestions of where or what to possibly look at as the culprit?

I have been having a problem with my 2001 GMC Sierra C3 for about 6 months now and am hoping someone can point me in the right direction to get it fixed. At low speed while making sharp turns I have vigorous shaking in what seems like the front. This truck is AWD all the time instead of push button 4WD. I initially thought it was a problem with my AWD, but a guy told me yesterday that it may have something to do with my transfercase. He suggested I drain it and put more fluid in. If the problem is not resolved after that I am to go take it in and have it reprogramed. Finally if this does not work I am to have some serious maintainence done. I am interested to see if any of you truck owners can point me in the right direction. I have had numerous work done over the last including a left ball joint and bearing and a UV joint replacement. I am hoping for a simple fix, but nothing seems to be simple or inexpensive with this truck. Please Help

Recently took my 04 Silverado ext cab 1500 to the snow and heard this growling noise in the front end when turning. Also smelled a burnt rubber smell after I stopped. After going back to 2 Hi no problems. It is a manual 4WD transfer case switch.

I have a 2000 gmc 1500 4x4. I took it to the snow this last weekend. I noticed when i got back it was making a noise. The only time it does it is when im backing up. I thought it might still be in 4 wheel drive but the front tires dont pull. I took out the front drive line but still makes the noise. It also feels like it dosnt have as much hores power. I dont have a hole lot of money to fix it. Is there some one who can help.

I have a 2000 gmc 1500 4x4. I took it to the snow this last weekend. I noticed when i got back it was making a noise. The only time it does it is when im backing up. I thought it might still be in 4 wheel drive but the front tires dont pull. I took out the front drive line but still makes the noise. It also feels like it dosnt have as much horse power. I dont have a hole lot of money to fix it. Is there some one who can help.

I have a 1995 Chevy Cheyenne 1500 4x4 ExtCab 5speed standard, it has a manual floor shifter, when I put the shifter into high 4x4 it wont engage and no light, but when I put it into low 4x4 it engages but still no light comes on...this is frustrating..any answers would be greatly appreciated, thanks.

Hi I have the same problem I think. My splines look fine though on the two shafts. I have been through the entire front-end and cannot find anything else. May I ask how you discovered your problem and which part(s) you are planning on replacing? Is there any way the actuator is not engaging fully in your opinion? If you have already fixed your 4 wheel drive what was it? on my truck the sprocket that is moved by the actuator to join the shafts seems a little worn on one end. is yours like that? Thanks for any help! I'll let you know what we end up doing as well.~Ben

I have a 2004 GMC 1500 auto. trans. with 4wheel drive shifter on the hump. Manual says i can shift from 2 hi to 4 hi anytime below something like 45 mph. More often than not when i have tried to do that i get a clashing of gears. Sometimes it shifts just fine,other time is doesn't. Shifting seems to be temp. related also. I know the manual says i can shift while moving,but the clashing makes me nervous. I have been stopping and shifting in and out of 4 wheel with no issues. Am i overly concerned,or is my technique wrong. :confuse: Thanks

I've been reading at various sites about problems with GMC 4x4 performance in snow. Many people seem to be saying that no matter what they do they can't get decent traction. Most of this seems to be related to not having locking differentials at both ends of the truck. I know that none is offered for the front but a friend of mine said that the traction problems are considerably reduced when you have the locking rear AND the StabiliTrak option (with Traction Control). Is anyone able to confirm that their 4x4 truck with these options does well in snow and also those without BOTH of these options do NOT do well? I am considering a GMC for my retirement vehicle and it will see lots of snow in western Montana. I don't want to end up with a "2x3" as some have dubbed these poor perfomers because one front wheel gets no traction and brings the rig to a halt. Any other suggestions are welcome for a good snow truck. I notice that StabiliTrak is not available on the 2500 or 3500 for some reason(?). Thanks.

I have the same model 1995 truck with auto transmission and manual transfer shift. When I shift the transfer into 4hi or 4lo the light on the transfer shifter does not come on, and the front wheels will not turn. The front drive shaft turns but no power to the front wheels. Did you find out what the problem was with yours?Anyone else know?

Thanks it is auto. There is a fitting on the front axle differntial that has two wires going to it. There is some dammage to the wires but they don't seem to be broken. I can't tell how the fitting is removed from the differntial if that is the problem.